C# Enum - How to Compare Value

Question

How can I compare the value of this enum

public enum AccountType
{
    Retailer = 1,
    Customer = 2,
    Manager = 3,
    Employee = 4
}

I am trying to compare the value of this enum in an MVC4 controller like so:

if (userProfile.AccountType.ToString() == "Retailer")
{
    return RedirectToAction("Create", "Retailer");
}
return RedirectToAction("Index", "Home");

I also tried this

if (userProfile.AccountType.Equals(1))
{
    return RedirectToAction("Create", "Retailer");
}
return RedirectToAction("Index", "Home");

In each case I get an Object reference not set to an instance of an object.

Answer 1

use this

if (userProfile.AccountType == AccountType.Retailer)
{
     ...
}

If you want to get int from your AccountType enum and compare it (don't know why) do this:

if((int)userProfile.AccountType == 1)
{ 
     ...
}

Objet reference not set to an instance of an object exception is because your userProfile is null and you are getting property of null. Check in debug why it's not set.

EDIT (thanks to @Rik and @KonradMorawski) :

Maybe you can do some check before:

if(userProfile!=null)
{
}

or

if(userProfile==null)
{
   throw new ArgumentNullException(nameof(userProfile)); // or any other exception
}

Answer 2

你可以使用Enum.Parse ，如果它是字符串

AccountType account = (AccountType)Enum.Parse(typeof(AccountType), "Retailer")

Answer 3

Comparision:

if (userProfile.AccountType == AccountType.Retailer)
{
    //your code
}

In case to prevent the NullPointerException you could add the following condition before comparing the AccountType :

if(userProfile != null)
{
    if (userProfile.AccountType == AccountType.Retailer)
    {
       //your code
    }
}

or shorter version:

if (userProfile !=null && userProfile.AccountType == AccountType.Retailer)
{
    //your code
}

Answer 4

You can use extension methods to do the same thing with less code.

public enum AccountType
{
    Retailer = 1,
    Customer = 2,
    Manager = 3,
    Employee = 4
}

static class AccountTypeMethods
{
    public static bool IsRetailer(this AccountType ac)
    {
        return ac == AccountType.Retailer;
    }
}

And to use:

if (userProfile.AccountType.isRetailer())
{
    //your code
}

I would recommend to rename the AccountType to Account . It's not a name convention .

Answer 5

You should convert the string to an enumeration value before comparing.

Enum.TryParse("Retailer", out AccountType accountType);

Then

if (userProfile?.AccountType == accountType)
{
    //your code
}